1. Field of the Invention
The present invention relates to an IPv6 network, and more particularly, to a method of advertising an address of a domain name service (DNS) server present on an IPv6 network, and a routing method thereby.
2. Description of the Related Art
The Internet is composed of autonomous systems that are operated by a network manager. The network manager may be an Internet service provider (ISP), a school, or a company. The group of autonomous systems forms the Internet in a hierarchical structure. Routing protocols for exchanging routing information between routers within one autonomous system are called interior gateway protocols (IGPs), and routing protocols for exchanging routing information between a plurality of autonomous systems are called exterior gateway protocols (EGPs). Examples of the IGPs include routing information protocols (RIPs) and open shortest path first (OSPF) protocols. An example of the EGPs is border gateway protocols (BGPs).
The OSPF protocols are typical link-state protocols. Routers used in the OSPF protocols exchange topologies and link states of their local links with other routers to form a topology of an overall network. All routers within a routing domain of a pertinent network have the same information on the configured network topology, and perform routing using information on the network topology.
Here, information that describes topologies and link states of local links and the exchange of the topologies and link states with other routers is called a link-state advertisement (LSA). A procedure of continuously forwarding LSAs to other routers is called flooding. Information on the overall network obtained using the forwarded LSAs is referred to as a link state database.
When a network is an IPv6 network, even though a user does not set Internet protocol (IP) addresses, network equipment connected to the IPv6 network can receive a router advertisement (RA) message from routers and automatically set the IP addresses using network prefix information contained in the message. Accordingly, a user interface does not need to be used for setting up a network.
Although the IP addresses are automatically set using the prefix information contained in the RA message, domain name service (DNS) servers are not automatically set and have to be manually set one by one. When one of the set DNS servers is out of order and hence cannot operate, other DNS servers have to be manually set one by one.